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[ Upstream commite2c6939341] In __icmp_send() there is a possibility that the rt->dst.dev is NULL, e,g, with tunnel collect_md mode, which will cause kernel crash. Here is what the code path looks like, for GRE: - ip6gre_tunnel_xmit - ip6gre_xmit_ipv4 - __gre6_xmit - ip6_tnl_xmit - if skb->len - t->tun_hlen - eth_hlen > mtu; return -EMSGSIZE - icmp_send - net = dev_net(rt->dst.dev); <-- here The reason is __metadata_dst_init() init dst->dev to NULL by default. We could not fix it in __metadata_dst_init() as there is no dev supplied. On the other hand, the reason we need rt->dst.dev is to get the net. So we can just try get it from skb->dev when rt->dst.dev is NULL. v4: Julian Anastasov remind skb->dev also could be NULL. We'd better still use dst.dev and do a check to avoid crash. v3: No changes. v2: fix the issue in __icmp_send() instead of updating shared dst dev in {ip_md, ip6}_tunnel_xmit. Fixes:c8b34e680a("ip_tunnel: Add tnl_update_pmtu in ip_md_tunnel_xmit") Signed-off-by: Hangbin Liu <liuhangbin@gmail.com> Reviewed-by: Julian Anastasov <ja@ssi.bg> Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.